Solenoid gas valve

ABSTRACT

A solenoid valve has a main body defining a gas inlet passage, a gas outlet passage, and a cavity; a core tube forming a closure for said the cavity so as to prevent an escape of gas; a cylindrical main piston slidably movable in said the cavity of said the main body, said the main piston forming a front chamber and a back chamber in said the main body, said the main piston having a gas conduit for passing the gas from said the gas inlet passage to said the front chamber and an axial hole for passing the gas from said the back chamber into said the gas outlet passage with a bleed orifice at one end of said the axial hole; said the main piston being spring biased to a closed position; a spring biased pilot piston; and an electrical coil means associated with said the core tube to provide a magnetic field for movements of said the pilot piston and said the main piston, so that when said the coil means is deenergized said the pilot piston closes said the outlet passage and causes a pressure equalization allowing said the return spring to push said the main piston to close the valve, while when said the coil means is energized said the pilot valve opens said the outlet passage and lowers a pressure which causes pushing of said the main piston to open the valve.

BACKGROUND OF THE INVENTION

The present invention relates generally to solenoid gas valves, and moreparticularly to a dual active pistons solenoid gas valve, in particularfor alternative fuels vehicles.

In vehicles that run on gaseous alternative fuels, such as natural gasor hydrogen, the fuel is normally stored in a high-pressure tank, and avalve is utilized to open and close access to conduits, along which suchhigh-pressure gaseous fluids flow from a storage tank to a vehicleengine. Typically such valves are of the solenoid type.

Solenoids of a reasonable size can typically produce a pulling forcethat is approximately only 1/100 of the force necessary to unseat avalve that is being forced shut by the high-pressure gasses. To overcomethis, most of the gas valves adapt a two-stage process in which a small“bleed” orifice is first opened, allowing the high-pressure gas from thestorage tank to flow through the “bleed” orifice and into a downstreamoutlet passage way that leads the engine. As the downstream outletpassage way fills up with gas, the pressure will increase, subsequentlygradually reducing the force necessary to unseat the closed valve.Eventually, the differential pressure between the upstream anddownstream passage ways becomes so small as to allow the valve to beopen by the relatively weak pull of the solenoid valve, thus resultingin the flow of high-pressure gas from the storage tank to the vehicleengine.

One of the main problems with the above described system is the lengthof time required for the downstream chamber to fill with a sufficientvolume of high-pressure gas, so that the solenoid can unseat the mainvalve. This problem is exasperated in large vehicles, such as buseswhere the gaseous fuel storage tank can be several meters away from theengine and therefore, it may take an unacceptable period of time for thepassageway downstream of the valve to fill up to the point when thesolenoid can unseat the main valve. These valves are alsodisadvantageous in vehicles that are bi-fueled by gasoline and naturalgas or dual-fueled by diesel fuel and natural gas. When these vehiclesswitch over from liquid fuel to natural gas, there can be a conspicuousloss in power output over an unacceptable period of time, while thepassage way downstream of the valve fills up with natural gas.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide asolenoid gas valve of the above mentioned general type which avoids thedisadvantages of the prior art.

It is also an object of the present invention to provide a solenoid gasvalve which has an intrinsic ability to shut off gas flow when a batteryvoltage is diminishing, so that when the battery becomes weaker, thepull on the pilot piston will weaken accordingly allowing it to close,so as to provide equalization of pressures in two chambers and sealingof the main piston, to stop the flow of gaseous fuels to the engine whenthe battery expires and the vehicle stops running.

It is also another object of the present invention to provide a solenoidgas valve that will virtually open and close instantaneously, once thesolenoid coil is energized, so that a very rapid and immediate openingof the valve to a wide-open position is performed.

It is also another object of the present invention to provide a solenoidgas valve in which there is no reliance on the built-up pressure withina downstream outlet passage way as a means for operating the valve, sothat the inventive solenoid gas valve can operate soundly and rapidlyindependently from the pressure in the downstream outer passage way.

In keeping with these objects and with others which will become apparenthereinafter, one feature of present invention resides, briefly stated ina solenoid gas valve which has a main body defining a gas inlet passage,a gas outlet passage, and a cavity; a core tube forming a closure forsaid cavity so as to prevent an escape of gas; a cylindrical main pistonslidably movable in said cavity of said main body, said main pistonforming a front chamber and a back chamber in said main body, said mainpiston having a gas conduit for passing the gas from said gas inletpassage to said front chamber and an axial hole for passing the gas fromsaid back chamber into said gas outlet passage with a bleed orifice atone end of said axial hole; said main piston being spring biased to aclosed position; a spring biased pilot piston; and electrical coil meansassociated with said core tube to provide a magnetic field for movementsof said pilot piston and said main piston, so that when said coil meansis deenergized said pilot piston closes said outlet passage and causes apressure equalization allowing said return piston to push said mainpiston to close the valve, while when said coil means is energized saidpilot valve opens said outlet passage and lowers a pressure which causespushing of said main piston to open the valve.

When the solenoid gas valve is designed in accordance with the presentinvention, it avoids the disadvantages of the prior art and provides forthe above-specified advantages. The novel features which are consideredas characteristic for the present invention are set forth in particularin the appended claims. The invention itself, however, both as to itsconstruction and its method of operation, together with additionalobjects and advantages thereof, will be best understood from thefollowing description of specific embodiments when read in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial sectional view through a valve in accordance with thepresent invention, in a closed condition;

FIG. 2 is a partial axial sectional view of the valve of FIG. 1

FIG. 2A is a view along A-A of FIG. 2;

FIG. 3 is a view substantially similar to the view of FIG. 2, butshowing the inventive valve when a solenoid coil is not energized;

FIG. 4 is an axial sectional view of the inventive valve when solenoidcoil has been energized; and

FIG. 5 is a view showing the inventive valve when a main piston is open.

A rapid action solenoid gas valve in accordance with the presentinvention is illustrated in FIGS. 1-5. FIGS. 1 and 2 describe parts thatmake up the solenoid gas valve. A coil 1 and yoke 2 are mounted on acore assembly tube with a screw 3. The core assembly includes a stop 4,a tube 5 and the core, and the core includes a flange 6. A magneticcircuit is formed by a guide bushing 26 and a molded pilot piston 9,both being constructed from ferromagnetic material. The core-assembly,to which is secured the coil and yoke, is threaded into a housing 51 ofa main body. An O-ring 7 is provided at the junction of thecore-assembly and the main body 50. The main body 50 is connected to aninlet chamber 16, which fills a front chamber 25 with high-pressure gasvia an orifice 28 connected to an opening 29 in a spacer 21. A drilledhole 23 connects the valve outlet to an opening leading to a downstreampassageway 24.

A main piston 19 controls the main stream by sliding up and down withina rubber sleeve 13. The valve shuts off when the main piston 19 slidesdown pressing against a seal 20, and opens when the main piston 19slides away from the seal 20. An O-ring 22 is provided underneath theseal in order to prevent gas leakage. A threaded nut 14 holds the spacer21 and seal 20 in place. An insert 18 with an axial through-hole 30 ispressed into a cylindrical cavity 32 of the main piston 19 allowinghigh-pressure gas flows into the back chamber 15. An appropriate sealantis placed around an insert 18 to avoid gas leakage into the interstitialspaces between the main piston 19 and the front chamber 25. The corealso presses the rubber sleeve 13 that prevents gas leakage into a backchamber 15 from surrounding space. High-pressure gas flows from thefront chamber 25 to the back chamber 15 via a network of spaces,orifices and passageways (36, 30, 31, 32 and 33). The axial through-hole30 limits the high-pressure gas flow when the valve is opened and thathelps to create the pressure difference between the two chambers. Aninterference fit between the main piston 19 and the rubber sleeve 13also prevents gas flow axially between the two chambers via theinterstitial spaces between the main piston 19 and the rubber sleeve 13.

When the coil 1 is energized, the pilot piston 9 opens and high-pressuregas from the back chamber 15 bleeds out of the valve through anothernetwork of orifices and passageways (35, 27, 23, and 24). A drainorifice 35 and a passageway 27 are drilled into the main piston 19, andthey lead to the valve outlet. A return spring 11 inside the coreapplies a force against the main piston 19 so that it closes tightly.Guide bushing 26 is made of ferromagnetic material and threaded with themain piston 19 to provide a pilot piston chamber 38 to guide themovement of the sliding pilot piston 9. Another hole 34 is provided toconnect the back chamber 15 to the pilot piston chamber 38. One end ofthe pilot piston 9 is molded with sealing material 10. A pilot pistonspring 8 attached to the stop 4 supplies the force necessary to keep thepilot piston 9 closed when the solenoid is inactive.

The solenoid valve in accordance with the present invention operates inthe following manner.

FIG. 1 is an axial sectional view through a valve constructed inaccordance with this invention. FIG. 1 shows the valve in the “closed”condition. In FIG. 2 the solenoid coil is not energized and the frontchamber 25 fills up with high-pressure gas. At the same time,high-pressure gas flows into the back chamber 15 through the gap betweenthe main piston 19 and the spacer 21 and then through a chamber 36 andan axial through-hole 30. The gas makes its way to the back chamber 15through the series of orifices and passageways (31, 32 and 33). Hole 34is provided so that the gas of the back chamber 15 flows into the pilotpiston chamber 38. At this point, in FIG. 3, while the coil is notenergized, the gas pressure on both sides of the main piston 19 isequal. In FIG. 4 the solenoid coil has been energized. The pilot piston9 is attracted by the magnetic force and is pulled towards the stop 4.The gas in the back chamber 15 will subsequently bleed through the drainhole 35 and be released downstream 24 via the network of passageways 27,23.

Once the gas in the back chamber 15 is released downstream 24, the forceresulting from the pressure difference between the front 25 and backchamber 15 becomes greater than the force of the return spring 11, whichresults in opening the main piston 19, as shown in FIG. 5. The guidebushing 26 is attracted by the magnetic force from the stop 4 and thepilot piston 9 is keeping open the drain orifice 35. The magnetic forcebetween the stop 4 and the guide bushing 26 can avoid the abruptshot-off of the main piston 19 in the event of abrupt change in thepressure difference between the front chamber 25 and the back chamber15.

When the solenoid magnetic coil is no longer energized, the pilot pistonseals against the drain orifice 35, allowing the pressure between thefront 25 and back chamber 15 to equalize again as gas continues to flowinto the back chamber 15 through the axial through hole 30. The mainpiston 19 is consequently forced by the return spring 11 to closeagainst the seal 20, thus seizing the flow, and the valve returns to thecondition shown in FIGS. 1, 2 and 3.

It will be understood that the elements described above may also beusefully applied in other types of constructions differing from the typedescribed in detail above.

While the invention and description have been illustrated and embodiedin a solenoid gas valve, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. A solenoid gas valve constructioncomprising: a main body defining an inlet, an outlet and a cavitycommunicating with both the inlet and outlet; a tubular core comprisingan inwardly directed annular flange and disposed in the cavity, a tubesurrounding the core, a stop occluding the end of the tube, an o-ringmounted about the core and sealing the core to the main body; a threadednut, a spacer, a seal and a sleeve defining, in combination with thecore, a main piston chamber; a guide bushing having communicationconduit holes locating circumferentially thereon, the guide bushingbeing in abutment at one end with the stop such that a pilot pistonchamber is defined by the guide bushing, the core and the stop; a mainpiston comprising an end, a recess portion, and a cylindrical body, themain piston being connected to the other end of said guide bushing and,together with said guide bushing, being slidably movable in said mainpiston chamber; said main piston segregating said main piston chamber toa front chamber and a back chamber, said main piston further having anaxial passage including a drain orifice extending therethrough providingfor communication between the pilot piston chamber and the outlet, themain piston further having a cavity located at an outer circumferentialportion of the main piston to communicate with the front chamber and apassage connecting said cavity to said back chamber; a pilot pistonslidably movable in said pilot piston chamber; an insert, having anaxial through hole and disposed in said cavity, places into saidcylindrical cavity of said main piston; the diameter of the axialthrough hole being smaller than that of said drain, the through-hole andpassage defining a gas passage from said front chamber, to said backchamber; a return spring received within said back chamber between saidmain piston and said inwardly-directed annular flange of said core, tourge said main piston in a direction away from said core, so that saidspherical end of said main piston presses against said valve seat toclose the communication between the inlet and outlet; and a pilot pistonspring biasing to urge said pilot piston in a direction away from saidstop of said core, so that the pilot piston presses against said drainorifice of said passage to achieve a gas-tight seal.
 2. A solenoid gasvalve as defined in claim 1 wherein the main body has a central axis,the inlet extends perpendicular to the central axis and the outletextends along the central axis.
 3. A solenoid gas valve as defined inclaim 1 wherein the annular flange and stop are ferromagnetic and thetube is non-ferromagnetic.
 4. A solenoid gas valve as defined in claim 1wherein the spacer has circumferential openings to communicate betweenthe inlet and the front chamber.
 5. A solenoid gas valve as defined inclaim 1 wherein the guide bushing is ferromagnetic.
 6. A solenoid gasvalve as defined in claim 1 wherein the surface of the end of the mainpiston is spherical and smooth and the cylindrical body of the mainpiston is spherical and smooth.
 7. A solenoid gas valve as defined inclaim 1 wherein said return spring is a compression spring.
 8. Asolenoid gas valve as defined in claim 1 wherein said pilot pistonspring is a compression spring.
 9. A valve comprising: a valve bodyhaving an inlet (16) and a downstream passageway (24) and a cavitycommunicating with each of the inlet and downstream passageway (24), thecavity including a front chamber (25) and a back chamber (15); asolenoid coil (1); a main piston (19) mounted for reciprocating movementin the valve body, the main piston having: a passageway (27) terminatingin an orifice (35); being exposed to the front chamber (25) and the backchamber (15); and a guide portion (26); a pilot piston (9) constructedfrom ferromagnetic material and mounted for reciprocating movement inthe guide portion (26); a return spring (11) biasing the main piston(19) to a position which blocks flow between the inlet (16) and thedownstream passageway (24); a pilot piston spring (8) biasing the pilotpiston (9) towards a position which blocks the orifice (35); wherein thevalve is adapted such that when the coil (1) is energized, the pilotpiston (9) is urged by the coil (1) away from the position which blocksthe orifice, to allow gas from the back chamber (15) to bleed out of thevalve through the orifice (35) and passageway (27); when the main piston(19) is in the position which blocks flow between the inlet (16) and thedownstream passageway (24) and the coil (1) is not energized, the frontchamber (25) and back chamber (15) are in fluid communication with theinlet (16); when gases in the back chamber (15) are bled from the valvevia the orifice (35) and passageway (27), force resulting from thepressure difference between the front chamber (25) and back chamber (15)becomes greater than the force of the return spring (11), which resultsin the movement of the main piston (19) away from the position whichblows flow between the inlet (16) and the downstream passageway (24),thereby allowing flow through the valve; when the coil (1) is notenergized, the pilot piston (9) seals against the orifice (35), allowingthe pressure between the front chamber (25) and back chamber (15) toequalize, whereupon the main piston (19) is forced by the return spring(11) to the position which blocks flow through the valve.
 10. A valveaccording to claim 9, wherein the guide portion (26) is ferromagneticand, when the coil (1) is energized, is biased by the coil (1) away fromthe position which blows flow between the inlet (16) and the downstreampassageway (24), thereby to avoid shut-off of the main piston in theevent of an abrupt change in pressure.